Reduction of petroleum nitrogen bases



Patented Nov. 17, 1942 REDUCTION OF PETROLEUM NITROGEN BASES v John T. Rutherford, Berkeley, Calif., assignor t e Standard Oil Company ofCalifornia, cisco, Calif., a corporation rip1a a'r Fran- No Drawing. App ication December 18', i939,

Serial No. 309,3 2. 1

hydrogenated from the unhydrogen'a'ted' products of reaction,

Although the existence of nitrogen bases in crude petroleums and their cracked and uncracked products has long since been ascertained, and although they have indeed been separated from the hydrocarbon oils Whichthjey accompany, in many refinery oil purificationopera tions, the bases themselves have .not herefore found any extensive use in the .arts and industries, in part because they are tertiary and weak ly basic in character and in part because they are made up of numerous members of vhoi r'1ologous series rather than ofa few individuals ,capable of easy separation. It has recently been found, however, that the corresponding secondary amines, prepared by suitable reducing methods, and various of the derivatives of the said. secondary amines, are of great utility inthe arts and industries, as they are stable, soluble in many organic solvents, and are stronglybasic in character.

It is accordingly a purpose of the invention to disclose and provide methods of reducing petroleum nitrogen bases to their corresponding secondary amines and of separating the reduced from the unreduced nitrogen compounds ,and

from neutral oil. Other objects and advantages of the invention will beapparent to those skilled in the art from adetailed discussion of the steps, conditions and elements embraced by the process thereof.

In the process, a crude nitrogen base-containing petroleum distillate of gasoline'ynaphtha .or kerosene character, cracked or uncracked, is extracted with a dilute mineral acid to formvvatersoluble salts of mixed nitrogen bases. These salts, in aqueous acid solution, are separated from the oils which had originally accompanied the bases, and are converted to andrecoveied as crude bases by neutralization of. the aqueousga'eid solution. The crude bases are then subjected 'to hydrogenation in the presence of a sulfactive hydrogenation catalyst, at elevated temperature and pressure and in the presence of an active sulfur carrier, to formthe corre'sponding secondamines are separated from tertiary (unchanged) amines and produced'hydrocarbon oil's by care,- ful adjustment of hydrogen'ion concentration. The unreduced bases are freed from hydrocarbons and returned ;to the hydrogenation system for substantially complete conversio to secondary amines."

The following exemplary procedures will illustrate the process ofitlieinvention in its detailed aspects. I 'A crude cracked naphtha, as obtained in the pyrogenetic cracking "of a nitrogen cont'aining crude petroleumf on "or distillate, "is extracted at ordinary temperatures with a dilute aqueous "sulfuric acid solution, of a concentration generally below about 50% 1 12804 and preferably'jalo out 30% H2804; water-soluble sulfates of mixed petroleum nitrogen bases are formed. The aquebus solutio'n'of ,these'salts is separated from the petroleum oil, by decantation, and the mixed petroleum nitrogen bases are recovered by decomposing the salts With a dilute aqueous alkali metal hydroxide solution, added tothe dilute sulfuric acid solution 'of the basic salts 'in'slight excess; the bases recovered are s'ufficiently Water-insoluble to permit of stratif cation" and decantation. 'In a typical case, a' mixture of the crude bases thus separated from a crudecr'acked 1005-500 F, naphtha or California petroleum origin hadaspecific gravityof 0.943, a basic dissoci ationconstant of LOX 10 an average molecular Weightof 1 50, and an A, S. TI. M. distillation boiling point'range (Method D-86) between 360 and,478 F."'(2 0% point, '38'2 50% point,,3$8; 90% point, 442" F.) it' had a sulfur content of 0.15% and'yvas 99% soluble man equal volume of' 3 0% s ulfuric acid.

The mixed nitrogen bases thus recovered are reduced to secondary amines by passage over molybdenum sulfid e,Moss; suitably deposited on activated charcoal; in the presence of hydrogen and at superatm'ospheric' temperature and, pressure,'accompanied by an active sulfur carrier such as carbondi'sulfid'l 'Iii'the' above typical case, the crude mixed'nitrogen bases referred t'o' Wer'e passed over'theeataiyst ata'rate' 'of 013 volume of liquid bases/volume of catalyst space/hour at an average catalyst temperature of 505 F., accompanied by hydrogen fed atthe rate of 33 moles/molof bases and also accompanied bycarbon ,disulfide fedat the rate of 1% by weight, of the bases; thej'catalyst' chamber was maintained at 3000 pounds per squareinch' hydrogen pressure. Aft'e'r' icondensationfand ar ami sma t .pcdse ise nida 5 gril i h whole i "i d u ted to a pH of approximately 9.5 by the careful addition of dilute aqueous sulfuric acid solution, upon which the reduced bases pass into aqueous solution as salts and the unreduced bases and produced neutral oil remain water-insoluble. The two layers thus formed are separated by decantation and dilute aqueous alkali metal hydroxide solution is added to the aqueous solution of the reduced salts, thus converting them to secondary amines which are sufficiently waterinsoluble to permit of Stratification and removal by decantation. In the above typical case, 56% by weight .of the mixed bases were recovered as secondary amines, 36% were recovered as imreduced bases, and 8% were recovered as hydrocarbon oil. The characteristics of the secondary amines were: specific gravity, 0.849; basic dissociation constant, 1.0 l average molecular weight, 146; A. S. T. M. distillation boiling point range, 340-412 F. point, 360; 50% point, 366; 90% point, 386 F.) solubility in sulfuric acid, 100%. i

In further exemplification of the several operating variables in the'process as described:

The temperature of reduction is best main- H tained at between about 475 and about 535 F.; 500-5l0 is optimum. At lower temperatures, conversion is incomplete; the table, based on operations conducted upon crude bases extracted from cracked petroleum naphtha, indicates that at higher temperatures the nitrogen bas heterocyclic nucleus is destroyed, yielding large amounts of hydrocarbons (and ammonia):

In general, increased hydrogen pressure improves the rate and degree of reduction, and a lowspace rate (volume liquid bases/volume catalyst/hour) is in most cases preferable. Best results are obtained when feeding about ten times the theoretically required proportions of hydrogen, that is, when feeding about 30 moles hydrogen per mol of cracked petroleum nitrogen base rather than the theoretically required -3 moles per mol, and when feeding up to about moles hydrogen per mol of uncracked petroleum nitrogen base rather than the theoretically required 5 moles per mol. The table illustrates the relationships between space rate, hydrogen feed and degree of reduction, in a system maintained at 200 atmospheres hydrogen pressure and oven temperature of 505 F., in operations carried out on cracked petroleum nitrogen bases.

Hydrogen iced Space Bases Bases Oil rate reduced unreduced Moles/mol Ou.1t.[bbl.

Per cent Per cent Per cent 0. 3 ll 10, 000 38 35 27 0.3 22 20, 000 47 47. 5 5. 5 0.3 33 30, 000 56 35. 5 8. 5

ascertained as dependent upon the introduction tion comprise the oxides and sulfides of the metals of Groups V and VI of the periodic system according to Mendeleeff, that is, of vanadium, co-

lumbium, tantalum, chromium, molybdenum, and

tungsten, alone or in admixture with each other or in admixture with the oxides or sulfides of the alkali metals, the alkaline earth metals, zinc and aluminum.

As exemplified in connection with the laboratory preparation of a molybdenum sulfide catalyst: Activated carbon is immersed in a solution prepared by dissolving 235 grams of molybdic acid in one liter of 15% ammonium hydroxide solution. Excess liquid is drained off and the solid is treated with hydrogen sulfide gas. Additional molybdate solution drains oil during the hydrogen sulfide treatment. After absorption of H28 is complete, the catalyst is dried in a stream of carbon dioxide. The dried catalyst is reduced for one hour with hydrogen at 600 F., at atmospheric pressure, and is then ready for use. In larger scale practice, the catalyst is sulfured in place in the reducing chamber under superatmospheric pressure and at temperatures of 500-600 by recycling hydrogen with additions of carbon disulfide; under these conditions the carbon disulfide is reduced to hydrogen sulfide, which may be used directly if desired. Other suitable methods of preparing catalysts which may be employed in the practice of the invention are disclosed in the specifications of United States Letters Patent Nos. 1,894,785, 1,955,253, 2,039,259, 2,045,795, 2,100,352, 2,112,292 and 2,123,623.

A particular feature of the invention lies in the separation of reduced bases from unreduced bases and produced hydrocarbons, by the addition of a dilute mineral acid, suitably aqueous 20-30% H2304, to the whole mixture of reduction products, until a pH of about 9.5 is reached. The aqueoussolution of the salts of the reduced bases is drawn -ofi,and dilute acid may again be added to the water-insoluble mixture of unreduced bases and oil, to further separate therefrom residual reduced bases; this extraction may be repeated if desired. The unreduced bases are then recycled to the reducing unit, either accompanied by produced hydrocarbon oil or separated therefrom by solution in excess dilute mineral acid, stratification and decantation of oil, and subsequent neutralization with dilute alkaline solution.

The process may be made continuous, throughout, by separating reduced from unreduced bases in a continuous counterflow tower and by continuously re-cycling unreduced bases, freed of hy drocarbon oils if desired, to the reducing system, together with further supplies of initial'crude bases and appropriate proportions of hydrogen and active sulfur carrier.

It will be understood that the precise characteristics of the secondary amines prepared in accordance with the invention will be dependent upon'the character of the cracked or uncracked petroleum oils or distillates from which the initial mixed petroleum nitrogen bases are recovered, as

well as upon the boiling point range of the-dis-f theproportions of at least 50 moles of hydrogen tillates and the, origin of the original petroleum stocks themselves. Generally, it is believed that the bases extractable from straight. run or uncracked distillates are largely mixtures. of alkylated quinoline homologues, while the bases-extractabl from-the thermally cracked distillates are largely mixtures ofalkylated pyridine homologues. Upon reduction in the manner hereinabove described, these bases are believed to yield mixtures of secondary amines, respectively, typified by the following structures in which the heterocyclic nuclei are saturated" and in which R represents one or 'more alkyl groups attached in the alpha, beta or gamma positions (probably the beta) R apparently has an average of about carbon atoms per molecule, but individual members of these homologous series may carry alkyl groups containing from one to about eight carbon atoms per chain.

The secondary amines prepared in accordance with the invention are useful in the preparation of rubber vulcanization accelerators and antioxidants, as metal pickling inhibitors and as intermediates in the preparation of extreme pressure lubricating agents, insecticides, and for the numerous purposes which secondary amines of this nature serve in the arts and industries.

I claim:

1. A process of preparing a homologous mixture of heterocyclic secondary amines having a basic dissociation constant higher than 1.O which comprises recovering from petroleum an initial mixture of petroleum nitrogen bases having the characteristics of tertiary amines and being substantially free of hydrocarbons and petroleum-derived impurities insoluble in an excess of 50% H2SO4, subjecting the said initial mixture of petroleum nitrogen bases to the action of hydrogen under reducing conditions, at temperatures within the range 475 and 535 F. and at superatmospheric pressure, in the presence of a sulfactive hydrogenating catalyst comprising molybdenum sulfide and in the presenc of an active sulfur carrier in proportions sufiicient to prevent material desulfurization of the catalyst, and separating produced secondary amines from the normally liquid reaction mixture by adjusting the pH of the said normally liquid reaction mixture to approximately 9.5.

2. A process as in claim 1, in which the initial mixture of petroleum nitrogen bases is recovered from an uncracked nitrogen-containing petroleum distillate and is substantially free of hydrocarbons and petroleum-derived impurities insoluble in an excess of 50% H2804, and in which the said initial mixture of petroleum nitrogen bases is subjected to the action of hydrogen in the proportions of at least 30 moles of hydrogen per average mol of bases.

3. A process as in claim 1, in which the initial mixture of petroleum nitrogen bases is recovered from a cracked nitrogen-containing petroleum distillate and is substantially free of hydrocarbons and petroleum-derived impurities insoluble in an excess of 50% H2804, and in which the said initial mixture of petroleum nitrogen bases is subjected to the action of hydrogen in from petroleum nitrogen bases, which petroleum nitrogen bases are substantially free of hydrocarbons and petroleum-derived impurities insoluble in an excess of 50% H2804, which comprises passing the said petroleum nitrogen bases in vapor form through a body of sulfactive hydrogenating catalyst essentially consisting of a compound selected from the class of the oxides and sulfides of vanadium, columbium, tantalum, chromium, molybdenum and tungsten, simultaneously introducing to the catalyst body hydrogen in the proportion of at least three moles :per average mol of bases, maintaining the catalyst body at a temperature within the range 475 F. and 535 F; and at superatmospheric pressure, condensing normally liquid reaction products and separating the produced secondary amines from unreduced nitrogen bases and hydrocarbon oils.

5. A process of preparing secondary amines from petroleum nitrogen bases, which petroleum nitrogen bases are substantially free of hydrocarbons and petroleum-derived impurities insoluble in an excess of 50% HzSOi, which comprises passing the said petroleum nitrogen bases in vapor form through a body of sulfactive hydrogenating catalyst essentially consisting of a compound selected from the class of the oxides and sulfides of vanadium, columbium, tantalum, chromium, molybdenum and tungsten, simultaneously introducing to the catalyst body hydrogen in the proportion of at least three moles per average mol of bases and an active sulfur carrier in proportions sufficient to prevent material desulfurization of the catalyst body, maintaining the catalyst body at a temperature within the range 475 F. and 535 F. and at superatmospheric pressure, condensing normally liquid reaction products and separating the produced secondary amines from unreduced nitrogen bases and hydrocarbon oils.

6. A process of preparing secondary amines from petroleum nitrogen bases, which petroleum nitrogen bases are substantially free of hydrocarbons and petroleum-derived impurities insol- 'uble in an excess of 50% H2804, which com prises passing the said petroleum nitrogen bases in vapor form through a body of sulfactive hydrogenating catalyst essentially consisting of a compound selected from the class of the oxides and sulfides of vanadium, columbium, tantalum, chromium, molybednum and tungsten, simultaneously introducing to the catalytic body'hydrogen in the proportion of at least three moles per overage mol of bases and an active sulfur carrier in proportions sufiicient to prevent material desulfurization of the catalyst body, maintaining nitrogen bases are substantially free of hydrocarbons and petroleum-derived impurities insoluble in an excess of 50% H2804, which comprises passing the said petroleum nitrogen bases in vapor form through a body of sulfactive hydrogenating catalyst essentially consisting of a compound selected from the class of the oxides and sulfides of vanadium, columbium, tantalum, chromium, molybdenum and tungsten, at a space rate of approximately 0.3 volumes of liquid bases per volume catalyst body per hour, simultaneously introducing to the catalyst body hydrogen in the proportions of at least ten moles per average mol of bases and carbon disulfide in amounts between 0.5% and 1.5% of the weight of the bases, maintaining the catalyst body at superatmospheric pressure and within the range 475 to 535 F., condensing normally liquid reaction products, and separating produced secondary amines from unreduced nitrogen bases and produced hydrocarbon oils by adjusting the pH of the normally liquid condensed reaction mixture to approximately 9.5.

8. A process as in claim 7 in which the petroleum nitrogen bases passed through the catalytic body under reducing'conditions are derived from an uncracked nitrogen-containing petroleum distillate and are substantially free of hydrocarbons and petroleum-derived impurities insoluble in an excess of 50% H2804, and in which the secondary amines ultimately recovered are largely comprised of alkylated piperidine homologues.

9. A process as in claim 7, in which the petroleum nitrogen bases passed through the catalytic body under reducing conditions are derived from a thermally cracked nitrogen-containing petroleum distillate and are substantially free of hydrocarbons and petroleum-derived impurities insoluble in an excess of 50% H2804, and in which the secondary amines ultimately recovered are largely comprised of alkylated decahydroquinoline homologues.

10. A process as in claim 7, in which the catalyst body comprises molybdenum sulfide.

JOHN T. RUTHERFORD. 

